It is known that the administration of certain compounds containing a pyrazine ring as a main nucleus inhibit blood platelet function, i.e. platelet aggregation. However, the activity of these compounds is too weak for effective platelet aggregation inhibition.
The inhibition of platelet function by tetramethylpyrazine is disclosed in Ka Kit Nui et al., Res. Comm. Chem. Pathol. and Pharmacol., 58, 3-14 (1987).
U.S. Pat. No. 4,123,613 discloses substituted pyrazine derivatives exhibiting activity as inhibitors of platelet aggregation. They are prepared by condensing 10-methoxy-16-dimethylergoline-8-beta-methanol tosylate with the sodium salt of a mercaptopyrazine or aminopyrazine.
U.S. Pat. No. 4,721,713 discloses a method of platelet aggregation inhibition by administering 2-hydroxy-3-isopropyl-5,6-dimethylpyrazine or a hydrate thereof.
Japanese Patent Application No. 88-025709 discloses 2-alkoxy-3,5,6-substituted-pyrazine derivatives useful in inhibiting platelet aggregation and promoting vasodilation.
Japanese Patent Application No. 88-053935 discloses 2,3-di:phenyl-5-benzyl-pyrazine derivatives useful in inhibiting platelet agglutination and the prevention of diseases caused by platelet agglutination.
European Patent Application No. 194,686 discloses the preparation and use of dihydropyrazine derivatives having platelet aggregation-inhibiting activity.
None of the references teach the compounds of the present invention.